Technical Abstract:
Concerns for climate change are expanding interest in greenhouse gas (GHG) emissions from all agricultural sectors; animal production systems are no exception. The focus of this overview is to compare emission factors among egg and meat bird poultry operations, specifically layer and broiler chickens. Though gaseous emission evaluation is still relatively novel compared to other poultry research areas (e.g. genetics, nutrition, and management), NH3 has long been the prevalent gas of interest in poultry production due to its negative effect on birds and farm workers in confinement facilities. Only in the last decade have GHG emissions begun to be reliably quantified for poultry houses. Significant variation exists among the assessed poultry gas emission factors, largely due to production system (layer vs. broiler) as well as type of housing within each production system. Attempts at mitigation usually include feed optimization, gas scrubbing technologies and/or chemical addition to bedding. Emission factors span from no detectable concentration to a maximum of 0.38 kg CH4/bird/yr and 0.155 kg N2O/bird/yr. Examples of other emission factors for broiler confinement only include 50 g NH3/bird/yr and 4.64 kg CO2/bird/yr. The scientific community is working diligently to promote communications that will enable standardization of methodologies as well as consistent reporting units so that research efforts can be compared across locations with optimal efficiency. Utilizing emission factors specifically for each production system or subcategory thereof will enhance the accuracy of emission inventories.